1. Field of the Invention
The present invention relates to a driving apparatus for driving a plurality of actuators of an ink jet recording device, and additionally relates to an ink jet printer including a plurality of actuators and a driving apparatus for driving the actuators.
2. Discussion of Related Art
There is known a piezoelectric-type ink jet recording head including a plurality of nozzles for ejecting ink; a plurality of pressure chambers communicating with the nozzles, respectively; and a plurality of piezoelectric actuators opposed to the pressure chambers, respectively. The pressure chambers also communicate with a common ink chamber for supplying the ink to each of the pressure chambers. Each of the piezoelectric actuators includes a piezoelectric element and two electrodes sandwiching the piezoelectric element. When respective electric potentials of the two electrodes sandwiching the piezoelectric element are equal to each other, i.e., an electric voltage equal to zero volt (i.e., 0 V) is applied across the two electrodes, the each piezoelectric actuator is not deformed. However, when the respective electric potentials of the two electrodes are not equal to each other, i.e., an electric voltage not equal to 0 V is applied to the two electrodes, the each piezoelectric actuator is so deformed as to decrease a volume of a corresponding one of the pressure chambers. Therefore, in the ink jet recording head, if an electric voltage equal to 0 V and subsequently an electric voltage not equal to 0 V are applied to each piezoelectric actuator, a corresponding one of the nozzles ejects a droplet of ink.
Japanese Patent Application Publication P2003-237078A1 discloses a piezoelectric-type ink jet recording head employing, as a piezoelectric-actuator driving method, a so-called “fill-before-fire” method. In this method, first, an electric voltage not equal to 0 V is applied, as a stand-by voltage, to each one of piezoelectric actuators so as to decrease a volume of a corresponding one of pressure chambers, and subsequently an electric voltage equal to 0 V is applied to the each actuator so as to produce a negative pressure in the one pressure chamber. The thus produced negative pressure propagates as a pressure wave from the one pressure chamber to a common ink chamber and, when the negative pressure reflects at the common ink chamber, the negative pressure obtains an inverted phase and returns as a positive pressure to the one pressure chamber. Then, at a timing when the positive pressure arrives at the one pressure chamber, an electric voltage not equal to 0 V is applied to the each actuator so as to decrease the volume of the one pressure chamber. Since the thus produced positive pressure overlaps the returning positive pressure, an increased positive pressure is produced in the one pressure chamber. Thus, owing to the “fill-before-fire” method, each nozzle can eject a droplet of ink at a high speed without needing to applying a high voltage to each actuator.